@Article{BragaRWJAWPVMBAMVMG:2017:AeCoDe,
author = "Braga, Ramon Campos and Rosenfeld, Daniel and Weigel, Ralf and
Jurkat, Tina and Andreae, Meinrat O. and Wendisch, Manfred and
P{\"o}schl, Ulrich and Voigt, Christiane and Mahnke, Christoph
and Borrmann, Stephan and Albrecht, Rachel I. and Molleker, Sergej
and Vila, Daniel Alejandro and Machado, Luiz Augusto Toledo and
Grulich, Lucas",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {The Hebrew
University of Jerusalem} and {Johannes Gutenberg-Universit{\"a}t}
and {Institut f{\"u}r Physik der Atmosph{\"a}re} and {Max Planck
Institute for Chemistry} and {Universit{\"a}t Leipzig} and {Max
Planck Institute for Chemistry} and {Johannes
Gutenberg-Universit{\"a}t} and {Johannes
Gutenberg-Universit{\"a}t} and {Johannes
Gutenberg-Universit{\"a}t} and {Universidade de S{\~a}o Paulo
(USP)} and {Max Planck Institute for Chemistry} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Johannes
Gutenberg-Universit{\"a}t}",
title = "Aerosol concentrations determine the height of warm rain and ice
initiation in convective clouds over the Amazon basin",
journal = "Atmospheric Chemistry and Physics Discussion",
year = "2017",
volume = "2017",
pages = "1--44",
abstract = "We have investigated how pollution aerosols affect the height
above cloud base of rain and ice hydrometeor initiation and the
subsequent vertical evolution of cloud droplet size and number
concentrations in growing convective cumulus. For this purpose we
used in-situ data of hydrometeor size distributions measured with
instruments mounted on HALO (High Altitude and Long Range Research
Aircraft) during the ACRIDICON-CHUVA campaign over the Amazon
during September 2014. The results show that the height of rain
initiation by collision and coalescence processes (Dr, in units of
meters above cloud base) is linearly correlated with the number
concentration of droplets (Nd in cm-3) nucleated at cloud base (Dr
\≈ 5·Nd). When Nd exceeded values of about 1000 cm-3, Dr
became greater than 5000 m, and particles of precipitation size
were initiated as ice hydrometeors. Therefore, no liquid water
raindrops were observed within growing convective cumulus during
polluted conditions. Furthermore, also the formation of ice
particles took place at higher altitudes in the clouds in polluted
conditions, because the resulting smaller cloud droplets froze at
colder temperatures compared to the larger drops in the unpolluted
cases. The measured vertical profiles of droplet effective radius
(re) were close to those estimated by assuming adiabatic
conditions (rea), supporting the hypothesis that the entrainment
and mixing of air into convective clouds is almost completely
inhomogeneous. Secondary nucleation of droplets on aerosol
particles from biomass burning and air pollution reduced re below
rea, which further inhibited the formation of raindrops and ice
particles and resulted in even higher altitudes for rain and ice
initiation.",
doi = "10.5194/acp-2016-1155",
url = "http://dx.doi.org/10.5194/acp-2016-1155",
issn = "1680-7367",
label = "lattes: 5379515759830546 14 BragaRWJAWPVMBAMVMG:2017:AeCoDe",
language = "en",
targetfile = "braga_aerosol.pdf",
urlaccessdate = "27 abr. 2024"
}